The invention relates to a control system and method for controlling a fueling amount of an engine during engine crank. More particularly, the invention relates to a control system and method that delivers a fuel injection amount during engine crank based on a barometric pressure determined from signals received from a global positioning system.
Known engines have long utilized open loop air-fuel control during engine crank when the engine is being started. In particular, an engine controller generally utilizes either a measured or estimated cylinder air charge (lbs. of air/cylinder) and a desired air-fuel ratio to determine a fuel injection amount (lbs. of fuel/cylinder) during engine crank.
Known engine control systems have also utilized mass air flow (MAF) sensors in the throttle body of an engine to determine the cylinder air charge. However, during engine crank, MAF sensors may not provide accurate measurements of mass air flow because the airflow rate is at a lower measurable range of the sensor. Thus, to determine the cylinder air charge during engine crank, known systems have utilized the engine speed, an intake throttle position, and a stored estimated barometric pressure to calculate the cylinder air charge, instead of utilizing the MAF sensor output signal.
The stored estimated barometric pressure value, however, is only updated when the engine is operated at high engine speeds and/or large intake throttle openings when an accurate estimated barometric pressure can be determined. When the vehicle is driven from a low altitude to a relatively high altitude with respect to sea level, the stored barometric pressure may not be updated if high engine speeds and/or large throttle openings are not obtained. Thus, when the engine is stopped and thereafter enters engine crank, the stored barometric pressure may have a large error with respect to the actual barometric pressure. Thus, because the cylinder air charge is determined based on the inaccurate stored barometric pressure, the cylinder air charge may have a large error with respect to the actual inducted cylinder air charge. In this case, the estimated cylinder air charge would be greater than the actual cylinder air charge. Thus, a greater amount of fuel than needed for stoichiometric combustion (i.e., a rich air-fuel mixture) would be injected into the engine cylinder, which may result in a xe2x80x9clong startxe2x80x9d condition or a xe2x80x9cno startxe2x80x9d condition of the engine. Further, the rich air-fuel mixture may result in increased hydrocarbon (HC) emissions from the engine and decreased fuel economy.
In order to obtain more accurate estimates of cylinder air charge during engine crank mode, other known systems have added a pressure sensor to measure the barometric pressure. However, adding the pressure sensor increases assembly time, component costs, and warranty costs.
The invention relates to a control system and method that delivers a predetermined fuel injection amount, based on a barometric pressure determined from signals received from an external source. The external source may comprise a global positioning system, a communication satellite, or a land-based communication station that transmits either position indicative signals or other signals indicative of the barometric pressure. The inventive method is preferably utilized during engine crank. However, the inventive method may also be utilized during closed loop air-fuel control of the engine after engine crank has been completed.
The method for controlling an internal combustion engine in a vehicle in accordance with first aspect of the present invention includes adjusting a fuel injection amount during engine crank based on an ambient barometric pressure, the barometric pressure determined from at least one signal received from at least one transmitter external from the vehicle. The signals may comprise signals that are indicative of an altitude of the vehicle. The altitude can be utilized to determine the barometric pressure based on a known relationship between altitude and barometric pressure. Alternately, the signals may be indicative of latitudinal and longitudinal position of the vehicle. The latitudinal position and longitudinal position may be correlated with stored elevational information to determine the altitude of the vehicle, and, the altitude may be used to calculate the barometric pressure as described above. Alternately, the latitudinal and longitudinal position may be correlated with stored barometric pressure information to determine the associated barometric pressure.
The control system for an internal combustion engine in accordance with a second aspect of the present invention includes a receiver receiving at least one signal from at least one transmitter external from the vehicle, the signal being indicative of barometric pressure. The control system further includes a controller operably connected to the receiver, the controller adjusting a fuel injection amount in the engine during engine crank responsive to the barometric pressure.
The control system and method for controlling an internal combustion engine in accordance with the present invention provides a substantial advantage over conventional systems and methods. When a receiver, such as a GPS receiver, is already installed in a vehicle, the method may accurately determine the barometric pressure based on at least one signal received from a global positioning system. Thus, an additional pressure sensor that would ordinarily be utilized to determine barometric pressure can be omitted from the vehicle. Further, once the barometric pressure is determined, the barometric pressure can be utilized to control a fuel injection amount during various engine operating conditions including engine crank. Because GPS signals allow for accurate barometric pressure readings to be calculated, the cylinder air charge and the fuel injection amount, determined based on the barometric pressure, can also be accurately determined. Thus, the inventive control system and method solves the potential problems of xe2x80x9cno startxe2x80x9d or xe2x80x9clong startxe2x80x9d conditions during engine crank at high altitudes due to an inadvertent rich air-fuel mixture being injected into the engine cylinders because of an inaccurate barometric pressure estimate.